The United States Department of Homeland Security plans to use Twitter and Facebook to warn citizens about threats with its new National Terrorism Advisory System. The new program will in part replace the old color-coded system, put in place following the 9/11 terrorist attacks, that’s being phased out.

The Associated Press reports:

The 19-page document, marked "for official use only" and dated April 1, describes the step-by-step process that would occur behind the scenes when the government believes terrorists might be threatening Americans. It describes the sequence of notifying members of Congress, then counterterrorism officials in states and cities and then governors and mayors and, ultimately, the public.

The document insists that terror warnings would only be issued "when appropriate," and only after the proper authorities have been alerted first. The implementation is said to take effect as soon as April 27.

Zeus Kerravala, an analyst at the Yankee Group, said the fact that the U.S. government is entrusting something as critical as terrorist alerts to Facebook and Twitter shows how important social networking sites have become to people's lives.

"There are hundreds of millions of people using Facebook and Twitter. For many of them, it's their primary communication tool," Kerravala said. "That means it's a great way to get information to a massive number of people. Maybe the best."